Thermoplastic elastomers having improved set and foams made therefrom

ABSTRACT

A thermoplastic vulcanizate prepared by a process comprising the steps of dynamically vulcanizing a vulcanizable rubber within a mixture that includes from about 15 to about 90 percent by weight of the rubber and from about 10 to about 85 percent by weight of a long-chain branched thermoplastic resin, where the long-chain branched thermoplastic resin is (i) an alpha-olefin polymer, (ii) a copolymer of an alpha-olefin and an alpha-omega-olefin diene, or (iii) a mixture thereof, where the long-chain branched thermoplastic resin is characterized by a weight average molecular weight from about 100,000 to about 600,000, a number average molecular weight from about 40,000 to about 200,000, a z-average molecular weight from about 400,000 to about 2,000,000, a &lt;g&#39;&gt;vis from about 0.2 to about 0.95, and a melt flow rate from about 0.3 to about 30 dg/min.

This application is a division of U.S. patent application Ser. No.09/771,044, filed Jan. 26, 2001 and now U.S. Pat. No. 6,433,090.

TECHNICAL FIELD

This invention is directed toward thermoplastic elastomers and processesfor making the same, as well as foams made from these thermoplasticelastomers. Specifically, the thermoplastic elastomers include a rubberthat is at least partially cured, a long-chain branched thermoplasticresin, and optionally a linear thermoplastic resin.

BACKGROUND OF THE INVENTION

Thermoplastic elastomers are known. They have many of the properties ofthermoset elastomers, yet they are processable as thermoplastics. Onetype of thermoplastic elastomer is a thermoplastic vulcanizate, whichmay be characterized by finely-divided rubber particles dispersed withina plastic. These rubber particles are crosslinked to promote elasticity.Thermoplastic vulcanizates are conventionally produced by dynamicvulcanization, which is a process whereby a rubber is cured orvulcanized within a blend with at least one non-vulcanizing polymerwhile the polymers are undergoing mixing or masticating at some elevatedtemperature, preferably above the melt temperature of thenon-vulcanizing polymer.

Thermoplastic vulcanizates are useful for forming molded articles suchas boots, seals, and like for use in the automotive, industrial, andconsumer markets. These uses require that the articles demonstrate lowset under both stress and strain. This is especially true in coldenvironmental conditions. Therefore, there is a continued need to lowerthe compression and tension set of thermoplastic vulcanizates withoutdeleteriously impacting the mechanical properties of the thermoplasticvulcanizate.

Thermoplastic vulcanizates can also be foamed to form cellular articlessuch as weather seals. Typically, a foaming agent is added to thethermoplastic vulcanizate and the composition is extruded at or abovethe melt temperature of the thermoplastic phase. These cellulararticles, however, have not always been competitive because they sufferfrom a relatively high compression set and high compression loaddeflection. As a result, their use, such as in weather seals, has beenlimited.

SUMMARY OF INVENTION

In general the present invention provides a thermoplastic vulcanizateprepared by a process comprising the steps of dynamically vulcanizing avulcanizable rubber within a mixture that includes from about 15 toabout 90 percent by weight of the rubber and from about 10 to about 85percent by weight of a long-chain branched thermoplastic resin, wherethe long-chain branched thermoplastic resin is (i) an α-olefin polymer,(ii) a copolymer of an α-olefin and an α-ω-olefin diene, or (iii) amixture thereof, where the long-chain branched thermoplastic resin ischaracterized by a weight average molecular weight from about 100,000 toabout 600,000, a number average molecular weight from about 40,000 toabout 200,000, a z-average molecular weight from about 400,000 to about2,000,000, a <g′>_(vis) from about 0.2 to about 0.95, and a melt flowrate from about 0.3 to about 30 dg/min.

The present invention also includes a thermoplastic vulcanizate preparedby a process comprising the steps of dynamically vulcanizing avulcanizable rubber within a mixture that includes the rubber and along-chain branched thermoplastic resin, where the long-chain branchedthermoplastic resin is (i) an α-olefin polymer, (ii) a copolymer of anα-olefin and an α-ω-olefin diene, or (iii) a mixture thereof, where thelong-chain branched thermoplastic resin is characterized by a <g′>_(vis)from about 0.2 to about 0.95, and a melt flow rate from about 0.3 toabout 30 dg/min.

The present invention further includes a thermoplastic vulcanizatecomprising a vulcanized rubber that has been vulcanized in thesubstantial absence of a peroxide curative, and a long-chain branchedthermoplastic resin.

The present invention still further includes a thermoplastic vulcanizatecomprising a vulcanized rubber, and from about 27 to about 40 percent byweight of a long-chain branched thermoplastic resin based upon the totalweight of the vulcanized rubber and the long-chain branchedthermoplastic resin.

The present invention also includes a foam profile prepared by a processcomprising the steps of foaming a thermoplastic vulcanizate, where thethermoplastic vulcanizate is prepared by a process comprising the stepof dynamically vulcanizing a rubber within a mixture that includes fromabout 15 to about 90 percent by weight of the rubber and from about 10to about 85 percent by weight of a thermoplastic component, where thethermoplastic component includes from about 5 to about 75 percent byweight of a long-chain branched thermoplastic resin and from about 95 toabout 25 percent by weight linear thermoplastic resin, where thelong-chain branched thermoplastic resin is (i) an α-olefin polymer, (ii)a copolymer of an α-olefin and an α-ω-olefin diene, or (iii) a mixturethereof, where the long-chain branched thermoplastic resin ischaracterized by a weight average molecular weight from about 100,000 toabout 600,000, a number average molecular weight from about 40,000 toabout 200,000, and a z-average molecular weight from about 400,000 toabout 2,000,000, a <g′>_(vis) from about 0.2 to about 0.95, and a meltflow rate from about 0.3 to about 30 dg/min.

The use of long-chain branched thermoplastic resins within thermoplasticvulcanizates has surprisingly improved the tension set and compressionset of the thermoplastic vulcanizates. Additionally, the use oflong-chain branched thermoplastic resins provides soft thermoplasticvulcanizates having improved foaming characteristics.

PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION

The thermoplastic vulcanizates of this invention include at least onecured rubber, at least one long-chain branched thermoplastic resin, andoptionally one or more linear thermoplastic resins. These thermoplasticvulcanizates can be foamed to form cellular articles by employing afoaming agent.

Any rubber or mixture thereof that is capable of being crosslinked orcured can be used as the rubber component. Reference to a rubber mayinclude mixtures of more than one rubber. Useful rubbers typicallycontain some degree of unsaturation in their polymeric main chain. Somenon-limiting examples of these rubbers include elastomeric copolymers,butyl rubber, natural rubber, styrene-butadiene copolymer rubber,butadiene rubber, acrylonitrile rubber, halogenated rubber such asbrominated and chlorinated isobutylene-isoprene copolymer rubber,butadiene-styrene-vinyl pyridine rubber, urethane rubber, polyisoprenerubber, epichlolorohydrin terpolymer rubber, and polychloroprene. Thepreferred rubbers are elastomeric copolymers and butyl rubber.

The term elastomeric copolymer refers to rubbery copolymers polymerizedfrom ethylene, at least one α-olefin monomer, and optionally at leastone diene monomer. The α-olefins may include, but are not limited to,propylene, 1-butene, 1-hexene, 4-methyl-1 pentene, 1-octene, 1-decene,or combinations thereof. The preferred α-olefins are propylene,1-hexene, 1-octene or combinations thereof. The diene monomers mayinclude, but are not limited to, 5-ethylidene-2-norbornene;1,4-hexadiene; 5-methylene-2-norbornene; 1,6-octadiene;5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene; 1,3-cyclopentadiene;1,4-cyclohexadiene; dicyclopentadiene; 5-vinyl-2-norbornene and thelike, or a combination thereof. The preferred diene monomers are5-ethylidene-2-norbornene and 5-vinyl-2-norbornene. In the event thatthe copolymer is prepared from ethylene, α-olefin, and diene monomers,the copolymer may be referred to as a terpolymer or even a tetrapolymerin the event that multiple α-olefins or dienes are used.

Elastomeric copolymers are commercially available under the tradenamesVistalon™ (Exxon Mobil Chemical Co.; Houston, Tex.), Keltan™ (DSMCopolymers; Baton Rouge, La.), Nordel™ IP (DuPont Dow Elastomers;Wilmington, Del.), ElastoFlo™ (Union Carbide; Danbury, Conn.), and Buna™(Bayer Corp.; Germany).

In one embodiment, the elastomeric copolymer is a terpolymer ofethylene, at least one α-olefin monomer, and 5-vinyl-2-norbornene. Thisterpolymer is advantageous when a peroxide curative is employed asdescribed in U.S. Pat. No. 5,656,693, which is incorporated herein byreference. This terpolymer is also advantageous when asilicon-containing curative is employed in the presence ofplatinum-containing catalyst as described in International PublicationNo. WO 98/38226, which is incorporated by reference. The terpolymerpreferably includes from about 40 to about 90 mole percent of itspolymeric units deriving from ethylene, and from about 0.2 to about 5mole percent of its polymeric units deriving from vinyl norbornene,based on the total moles of the terpolymer, with the balance comprisingunits deriving from α-olefin monomer.

The term butyl rubber refers to rubbery amorphous copolymers ofisobutylene and isoprene or an amorphous terpolymer of isobutylene,isoprene, and a divinyl aromatic monomer. These copolymers andterpolymers should preferably contain from about 0.5 to about 10 percentby weight, or more preferably from about 1 to about 4 percent by weight,isoprene. The term butyl rubber also includes copolymers and terpolymersthat are halogenated with from about 0.1 to about 10 weight percent, orpreferably from about 0.5 to about 3.0 weight percent, chlorine orbromine. This chlorinated copolymer is commonly called chlorinated butylrubber. While butyl rubber is satisfactory for the practice. of thisinvention, halogen-free butyl rubber containing from about 0.6 to about3.0 percent unsaturation is preferred, with butyl rubber having apolydispersity of about 2.5 or below being especially preferred. Butylrubbers are commercially prepared by polymerization at low temperaturein the presence of a Friedel-Crafts catalyst as disclosed within U.S.Pat. Nos. 2,356,128 and 2,944,576. Butyl rubber is commerciallyavailable from a number of sources as disclosed in the Rubber World BlueBook. For example, butyl rubber is available under the tradename PolysarButyl™ (Bayer; Germany) or the tradename Exxon Butyl™ (Exxon ChemicalCo.).

Long-chain branched thermoplastic resins, which may be referred toherein as LCB-plastics, can generally be described as high molecularweight, highly branched polymers. Reference to a LCB-plastic willinclude a LCB-plastic or a mixture of two or more LCB-plastics.

The LCB-plastics are (i) α-olefin polymers or (ii) copolymers ofα-olefins and α-ω-dienes. The α-olefin polymers may include combinationsof α-olefin units such as units deriving from propylene and ethylene.Likewise, combinations of α-ω-dienes may be used. The copolymers ofα-olefins and α-ω-diene copolymers may be referred to as diene-modifiedpolyolefin polymers.

The diene-modified polyolefin polymers contain a limited amount ofα-ω-diene units so that these units are dispersed throughout thebackbone of the polymer. Accordingly, the diene-modified polymerscontain from 0.005 to 2.00 mole percent polymeric units deriving fromdienes, preferably from 0.01 to about 1.0 mole percent polymeric unitsderiving from dienes, and more preferably from about 0.02 to about 0.1mole percent polymeric units deriving from dienes. The remainder of thepolymer will typically derive from α-olefins.

The LCB-plastics have a weight average molecular weight (M_(w)) fromabout 100,000 to about 600,000, a number average molecular weight(M_(n)) from about 40,000 to about 200,000, and a z-average molecularweight (M_(z)) from about 400,000 to about 2,000,000. More preferably,LCB-plastics have an M_(w) from about 200,000 to about 500,000, an M_(n)from about 50,000 to about 150,000, and an M_(z) from about 500,000 toabout 1,500,000. Even more preferably, LCB-plastics have M_(w) fromabout 220,000 to about 450,000, an M_(n) from about 60,000 to about120,000, and a M_(z) from about 600,000 to about 1,300,000. Themolecular weights provided within this specification refer to M_(w),M_(n), and M_(z) as determined by Gel Permeation Chromatography (GPC)with both polystyrene and low molecular weight polyethylene standards.

The LCB-plastics are highly branched polymeric molecules. Preferably,these polymeric molecules are characterized by having a viscosityaverage branching index, <g′>_(vis), of from about 0.2 to about 0.95,more preferably from about 0.3 to about 0.9, and even more preferablyfrom about 0.5 to about 0.85. The viscosity average branching index,<g′>_(vis), which is determined by using GPC-3D analysis (GPC-3D (TripleDetector): Differential Refractive Index, Light Scattering, Viscometry),is one measurement of the average branching index (<g′>) of a molecularweight distribution of polymers.

Those skilled in the art appreciate that the branching index, g′, at agiven molecular weight is determined according to the formulag′=[η]_(branched)/[η]_(linear), where [η]_(branched) is the viscosity ofa branched polymer at a given molecular weight slice, i, and[η]_(linear) is the viscosity of a known linear reference polymer at thegiven molecular weight slice, i. And, the average branching index, <g′>,of the entire polymer can be determined according to the formula<g′>=[η]_(branched)/ [η]_(linear), where [η]_(branched) is the viscosityof the branched polymer, and [η]_(linear) is the viscosity of a knownlinear reference polymer, where the branched and linear polymers havethe same molecular weight.

The viscosity average branching index (<g′>_(vis)) of the entire polymermay be obtained from the following equation:${\langle g^{\prime}\rangle}_{vis} = \frac{\sum{C_{i} \cdot \lbrack\eta\rbrack_{i}}}{\sum{C_{i} \cdot \left\lbrack {KM}_{i}^{\alpha} \right\rbrack}}$

where M_(i) is the molecular weight of the polymer, [η]_(i) is theintrinsic viscosity of the branched polymer at molecular weight M_(i),C_(i) is the concentration of the polymer at molecular weight M_(i), andK and α are measured constants from a linear polymer as described byPaul J. Flory at page 310 of Principles of Polymer Chemistry (1953), andthe summation is over all the slices in the distribution. The <g′>_(vis)values are obtained while the polymer is in dilute solution within 1,2,4trichlorobenzene, and the GPC-3D is calibrated with both polystyrene andlow molecular weight polyethylene standards, the light scatteringdetector with a series of polymers of known molecular weight, and thedifferential viscometer with a series of polymers of known intrinsicviscosities.

The LCB-plastics may range from amorphous polymers to highly crystallinepolymers, including semi-crystalline polymers. The melt temperature ofthe LCB-plastics should generally be lower than the decompositiontemperature of the rubber. Preferably, the melt temperature (T_(m)) isfrom about 140 to about 170° C., more preferably from about 145 to about168° C., and even more preferably from about 150 to about 165° C. Theglass transition temperature (T_(g)) is preferably from about −10 toabout 10° C., more preferably from about −5 to about 5° C., and evenmore preferably from about −2 to about 2° C. The crystallizationtemperature (T_(c)) should preferably be from about 90 to about 140° C.,more preferably from about 100 to about 135° C., and even morepreferably from about 105 to about 130° C.

The LCB-plastics generally have a melt flow rate that is below about 100dg/min. Preferably, the melt flow rate should be from about 0.3 to about30 dg/min, more preferably from about 0.4 to about 20 dg/min, and stillmore preferably from about 0.7 to about 5 dg/min, as determinedaccording to ASTM D-1238, condition L (2.16 kg, 230° C.).

LCB-plastics can be synthesized by a number of techniques including theuse of metallocene or Ziegler-type catalysis to form diene-modifiedpolyolefin polymers, or by treating conventional polymers with radiationor other appropriate treatment, e.g., peroxide treatment.

For example, LCB plastics can be prepared by polymerizing one or moreα-olefin monomers having at least 3 carbon atoms with at least oneα-ω-diene by using a metallocene catalyst. This synthetic method isdisclosed in U.S. Pat. No. 5,670,595, which is incorporated herein byreference.

Useful α-olefins include those having from 2 to 8 carbon atoms, morepreferably 3, 4, 5, or 6 carbon atoms, and most preferably 3 carbonatoms. Exemplary α-olefins include ethylene, propylene, 1-butene,1-hexene, 1-octene, 2-methyl-1-propene, 3-methyl-1-pentene,4-methyl-1-pentene, 5-methyl-1-hexene, and mixtures thereof.

The α-ω-dienes may be linear, cyclic, or multi-cyclic, and includeconjugated linear dienes and fused and non-fused cyclic dienes. Thedienes are preferably α-ω-dienes such as, but not limited to1,7-octadiene, 1,9-decadiene, 1,13-tetradecadiene, 1,8-nonadiene,1,10-undecadiene, 1,11-dodecadiene, 1,15-hexadecadiene,1,17-octadecadiene, and norbornadiene. More preferably, the dienes areselected from 1,7-octadiene, 1,9-decadiene, 1,13-tetradecadiene, andnorbornadiene. Most preferably, the dienes are selected from1,9-decadiene and 1,7-octadiene.

Any metallocene catalyst may be used to synthesize the diene-modifiedcopolymers. Metallocenes are generally represented by the formulaCp_(m)MR_(n)X_(q), where Cp is a cyclopentadienyl ring or derivativethereof, M is a group 4, 5, or 6 transition metal, R is a hydrocarbylgroup or hydrocarboxy group having from 1 to 20 carbon atoms, X is ahalogen or an alkyl group, and m is an integer from about 1 to about 3,n is an integer from 0 to 3, q is an integer from 0 to 3, and the sum ofm, n, and q is equal to the oxidation state of the transition metal. Themetallocene may be bridged or unbridged, and include hetero atoms in thestructure. Examples of particularly preferred metallocenes are discussedin U.S. Pat. Nos. 4,530,914; 4,871,705; 4,937,299; 5,124,418; 5,107,714;5,120,867; 5,278,119; 5,304,614; 5,324,800; 5,347,025; 5,350,723;5,391,790; and 5,391,789; EP. Pub. Nos. 591 756; 520 732; and 420 436;and WO Pub. Nos. 91/40257; 93/08221; 93/08199; and 94/01471. Each ofthese references are incorporated herein by reference. Particularlypreferred metallocene components are those that are stereorigid andcomprise a group 4, 5, or 6 transition metal. Examples includebis-cyclopentadienyl derivatives, such as bis-indenyl metallocene.

The diene-modified copolymers prepared with the foregoing metallocenecatalyst may be treated with radiation, such as E-beam irradiation, tocause chain extension. This radiation treatment will increase themolecular weight of the polymers and broaden their molecular weightdistribution.

Alternatively, LCB-plastic may be prepared by treating linearcrystalline polyolefins with ionizing radiation. This method isdisclosed in U.S. Pat. No. 4,916,198, which is incorporated herein byreference.

Still further, LCB-plastic may be prepared bypolymerizing α-olefins withan insoluble coordination catalyst system. This method is disclosed inU.S. Pat. No. 5,504,171, this is incorporated herein by reference.

In the broadest sense, the linear thermoplastic resins include thosethermoplastic resins that are not LCB-plastics. More specifically,linear thermoplastic resin is a solid, generally high molecular weightplastic material. Preferably, this resin is a semi-crystalline polymerresin, and more preferably a resin that has a crystallinity of at least25 percent as measured by differential scanning calorimetry. The melttemperature of these resins should generally be lower than thedecomposition temperature of the rubber. Reference to a thermoplasticresin will include a thermoplastic resin or a mixture of two or morethermoplastic resins.

Linear thermoplastic resins preferably have a weight average molecularweight from about 200,000 to about 600,000, and a number averagemolecular weight from about 80,000 to about 200,000. More preferably,these resins have a weight average molecular weight from about 300,000to about 500,000, and a number average molecular weight from about90,000 to about 150,000.

The linear thermoplastic resins preferably have a melt temperature(T_(m)) that is from about 150 to about 175° C., preferably from about155 to about 170° C., and even more preferably from about 160 to about170° C. The glass transition temperature (T_(g)) of these resins is fromabout −5 to about 10° C., preferably from about −3 to about 5° C., andeven more preferably from about 0 to about 2° C. The crystallizationtemperature (T_(c)) of these resins is from about 95 to about 130° C.,preferably from about 100 to about 120° C., and even more preferablyfrom about 105 to about 110° C. as measured by DSC at 10° C./min.

Preferably, the linear thermoplastic resins have a melt flow rate thatis less than about 10 dg/min, preferably less than about 2 dg/min, andstill more preferably less than about 1.0 dg/min.

Exemplary linear thermoplastic resins include crystallizablepolyolefins, polyimides, polyesters (nylons), and fluorine-containingthermoplastics. Also, the linear thermoplastic resins may includecopolymers of polyolefins with styrene such as styrene-ethylenecopolymer. The preferred thermoplastic resins are crystallizablepolyolefins that are formed by polymerizing α-olefins such as ethylene,propylene, 1-butene, 1-hexene, 1-octene, 2-methyl-1-propene,3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, and mixturesthereof. Copolymers of ethylene and propylene or ethylene or propylenewith another α-olefin such as 1-butene, 1-hexene, 1-octene,2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene,5-methyl-1-hexene or mixtures thereof is also contemplated. Thesehomopolymers and copolymers may be synthesized by using anypolymerization technique known in the art such as, but not limited to,the “Phillips catalyzed reactions,” conventional Ziegler-Natta typepolymerizations, and metallocene catalysis including, but not limitedto, metallocene-alumoxane and metallocene-ionic activator catalysis.

An especially preferred linear thermoplastic resin is ahigh-crystallinity isostatic or syndiotactic polypropylene. Thispolypropylene generally has a density of from about 0.85 to about 0.91g/cc, with the largely isotactic polypropylene having a density of fromabout 0.90 to about 0.91 g/cc. Also, high and ultra-high molecularweight polypropylene that has a fractional melt flow rate is highlypreferred. These polypropylene resins are characterized by a melt flowrate that is less than or equal to 10 dg/min and more preferably lessthan or equal to 1.0 dg/min per ASTM D-1238.

Any curative that is capable of curing or crosslinking the rubber may beused. Some non-limiting examples of these curatives include phenolicresins, peroxides, maleimides, and silicon-containing curatives.Depending on the rubber employed, certain curative may be preferred. Forexample, where elastomeric copolymers containing units deriving fromvinyl norbornene are employed, a peroxide curative maybe preferredbecause the required quantity of peroxide will not have a deleteriousimpact on the engineering properties of the thermoplastic phase of thethermoplastic vulcanizate. In other situations, however, it may bepreferred not to employ peroxide curatives because they may, at certainlevels, degrade the thermoplastic components of the thermoplasticvulcanizate. Accordingly, some thermoplastic vulcanizates of thisinvention are cured in the absence of peroxide, or at least in theabsence of an amount of peroxide that will have a deleterious impact onthe engineering properties of the thermoplastic vulcanizate, whichamount will be referred to as a substantial absence of peroxide. Inthese situations, phenolic resins or silicon-containing curative arepreferred.

Any phenolic resin that is capable of crosslinking a rubber polymer canbe employed in practicing the present invention. U.S. Pat. Nos.2,972,600 and 3,287,440 are incorporated herein in this regard. Thepreferred phenolic resin curatives can be referred to as resole resinsand are made by condensation of alkyl substituted phenols orunsubstituted phenols with aldehydes, preferably formaldehydes, in analkaline medium or by condensation of bi-functional phenoldialcohols.The alkyl substituents of the alkyl substituted phenols typicallycontain 1 to about 10 carbon atoms. Dimethylol phenols or phenolicresins, substituted in para-positions with alkyl groups containing 1 toabout 10 carbon atoms are preferred. These phenolic curatives aretypically thermosetting resins and may be referred to as phenolic resincuratives or phenolic resins. These phenolic resins are ideally used inconjunction with a catalyst system. For example, non-halogenated phenolcuring resins are preferably used in conjunction with halogen donorsand, optionally, a hydrogen halide scavenger. Where the phenolic curingresin is halogenated, a halogen donor is not required but the use of ahydrogen halide scavenger, such as ZnO, is preferred. For a furtherdiscussion of phenolic resin curing of thermoplastic vulcanizates,reference can be made to U.S. Pat. No. 4,311,628, which is incorporatedherein by reference.

An example of a preferred phenolic resin curative is defined accordingto the general formula (I).

where Q is a divalent radical selected from the group consisting of—CH₂—, —CH₂—O—CH₂—; m is zero or a positive integer from 1 to 20 and R′is an organic radical. Preferably, Q is the divalent radical—CH₂—O—CH₂—, m is zero or a positive integer from 1 to 10, and R′ is anorganic radical having less than 20 carbon atoms. Still more preferablym is zero or a positive integer from 1 to 5 and R′ is an organic radicalhaving between 4 and 12 carbon atoms.

Useful silicon-containing curatives generally include silicon hydridecompounds having at least two SiH groups. These compounds react withcarbon-carbon double bonds of unsaturated polymers in the presence of ahydrosilation catalyst. Silicon hydride compounds that are useful inpracticing the present invention include, but are not limited to,methylhydrogen polysiloxanes, methylhydrogen dimethyl-siloxanecopolymers, alkyl methyl polysiloxanes, bis(dimethylsilyl)alkanes,bis(dimethylsilyl benzene, and mixtures thereof.

Preferred silicon hydride compounds may be defined by the formula

where each R is independently selected from alkyls containing 1 to 20carbon atoms, cycloalkyls containing 4 to 12 carbon atoms, and aryls, mis an integer having a value ranging from 1 to about 50, n is an integerhaving a value ranging from 1 to about 50, and p is an integer having avalue ranging from 0 to about 6.

As noted above, hydrosilation curing of the elastomeric polymer ispreferably conducted in the presence of a catalyst. These catalysts caninclude, but are not limited to, peroxide catalysts and catalystsincluding transition metals of Group VIII. These metals include, but arenot limited to, palladium, rhodium, and platinum, as well as complexesof these metals. Platinum catalyst are preferred. For a furtherdiscussion of the use of hydrosilation to cure thermoplasticvulcanizates, reference can be made to U.S. Pat. No. 5,936,028, which isincorporated herein by reference. When silicon-containing curatives areemployed, the elastomeric copolymer employed will preferably include5-vinyl-2-norbornene as the diene component.

When used, peroxide curatives are generally selected from organicperoxides. Examples of organic peroxides include, but are not limitedto, di-tert-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide,α,α-bis(tert-butylperoxy)diisopropyl benzene, 2,5 dimethyl2,5-di(t-butylperoxy)hexane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, -butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide,lauroyl peroxide, dilauroyl peroxide,2,5-dimethyl-2,5-di(tert-butylperoxy)hexene-3, and mixtures thereof.Also, diaryl peroxides, ketone peroxides, peroxydicarbonates,peroxyesters, dialkyl peroxides, hydroperoxides, peroxyketals andmixtures thereof may be used. For a further discussion of peroxidecuratives and their use for preparing thermoplastic vulcanizates,reference can be made to U.S. Pat. No. 5,656,693, which is incorporatedherein by reference.

Plasticizers, extender oils, synthetic processing oils, or a combinationthereof may be employed in the compositions of the present invention.The extender oils may include, but are not limited to, aromatic,naphthenic, and paraffinic extender oils. The preferred syntheticprocessing oils are polylinear α-olefins. The compositions of thisinvention may include organic esters, alkyl ethers, or combinationsthereof. U.S. Pat. Nos. 5,290,886 and 5,397,832 are incorporated hereinin this regard. The addition of certain low to medium molecular weightorganic esters and alkyl ether esters to the compositions of theinvention dramatically lowers the T_(g) of the polyolefin and rubbercomponents, and of the overall composition, and improves the lowtemperature properties, particularly flexibility and strength. Theseorganic esters and alkyl ether esters generally have a molecular weightthat is generally less than about 10,000. It is believed that theimproved effects are achieved by the partitioning of the low T_(g) esterinto both the polyolefin and rubber components of the compositions.Particularly suitable esters include monomeric and oligomeric materialshaving an average molecular weight below about 2000, and preferablybelow about 600. The ester should be compatible, or miscible, with boththe polyolefin and rubber components of the composition; i.e., that itmixes with the other components to form a single phase. The esters foundto be most suitable were either aliphatic mono- or diesters oralternatively oligomeric aliphatic esters or alkyl ether esters.Polymeric aliphatic esters and aromatic esters were found to besignificantly less effective, and phosphate esters were for the mostpart ineffective.

In addition to the thermoplastic resins, rubber, curatives and optionalextender oils, the compositions of the invention may also includereinforcing and non-reinforcing fillers, antioxidants, stabilizers,rubber processing oil, lubricants, antiblocking agents, anti-staticagents, waxes, foaming agents, pigments, flame retardants and otherprocessing aids known in the rubber compounding art. These additives cancomprise up to about 50 weight percent of the total composition. Fillersand extenders that can be utilized include conventional inorganics suchas calcium carbonate, clays, silica, talc, titanium dioxide, carbonblack and the like.

Preferably, compositions of this invention will contain a sufficientamount of the rubber to form rubbery compositions of matter. The skilledartisan will understand that rubbery compositions of matter are thosethat have ultimate elongations greater than 100 percent, and thatquickly retract to 150 percent or less of their original length withinabout 10 minutes after being stretched to 200 percent of their originallength and held at 200 percent of their original length for about 10minutes.

Accordingly, the thermoplastic vulcanizates of the present inventionshould comprise at least about 25 percent by weight rubber. Morespecifically, the thermoplastic vulcanizates include from about 15 toabout 90 percent by weight, preferably from about 45 to about 85 percentby weight, and more preferably from about 60 to about 80 percent byweight rubber, based on the total weight of the rubber and thermoplasticcomponent.

The thermoplastic component of the thermoplastic vulcanizates includesan LCB-plastic or a combination of an LCB-plastic and linearthermoplastic resin. In other words, the thermoplastic vulcanizates mayexclusively include LCB-plastic as the thermoplastic component or mayinclude a blend of an LCB-plastic and linear thermoplastic resin as thethermoplastic component. In either event, the thermoplastic vulcanizatesshould generally comprise from about 10 to about 85 percent by weightthermoplastic component, which includes LCB-plastic or a blend ofLCB-plastic and linear thermoplastic component, based on the totalweight of the rubber and thermoplastic component combined. Preferably,thermoplastic vulcanizates comprise from about 15 to about 70 percent byweight, and more preferably from about 20 to about 50 percent by weight,thermoplastic component based on the total weight of the rubber andthermoplastic component combined.

Where the thermoplastic vulcanizate includes a blend of LCB-plastic andlinear thermoplastic resin, the thermoplastic resin component of thethermoplastic vulcanizate preferably contains from about 5 to about 75percent by weight LCB-plastic and from about 95 to about 25 percent byweight linear thermoplastic resin based upon the total weight of thethermoplastic component. More preferably, the thermoplastic vulcanizatecontains from about 15 to about 60 percent by weight LCB-plastic andfrom about 85 to about 40 percent by weight thermoplastic resin, andeven more preferably from about 25 to about 50 percent by weightLCB-plastic and from about 75 to about 50 percent by weight linearthermoplastic resin based upon the total weight of the thermoplasticcomponent. Surprisingly, thermoplastic vulcanizates that contain blendsof LCB-plastic and linear thermoplastic resin provide compositions thatcan be foamed into cellular materials that exhibit improved propertiessuch as compression set and compression load deflection.

Where extruded materials are desired that exhibit improved compressionset and improved melt strength, a greater amount of LCB-plastic may bedesirable. In these embodiments, the thermoplastic component of thethermoplastic vulcanizate preferably contains greater than 75 percent byweight LCB-plastic, more preferably greater than 90 percent by weightLCB-plastic, even more preferably greater than 95 percent by weightLCB-plastic, and still more preferably greater than 99 percent by weightLCB-plastic. In these embodiments, the thermoplastic vulcanizatespreferably contain from about 27 to about 40 percent by weightLCB-plastic based on the total weight of the rubber and LCB-plastic.More preferably, these thermoplastic vulcanizates include from about 30to about 38 percent by weight LCB-plastic, and even more preferably fromabout 33 to about 35 percent by weight LCB-plastic based on the totalweight of the rubber and LCB-plastic combined.

The skilled artisan will be able to readily determine a sufficient oreffective amount of vulcanizing agent to be employed without unduecalculation or experimentation. The amount of vulcanizing agent shouldbe sufficient to at least partially vulcanize the elastomeric polymer.Preferably, the elastomeric polymer is completely vulcanized.

Where a phenolic resin curative is employed, a vulcanizing amount ofcurative preferably comprises from about 1 to about 20 parts by weight,more preferably from about 3 to about 16 parts by weight, and even morepreferably from about 4 to about 12 parts by weight, phenolic resin per100 parts by weight rubber.

Where a peroxide curative is employed, a vulcanizing amount of curativepreferably comprises from about 1×10⁻⁴ moles to about 2×10⁻² moles, morepreferably from about 2×10⁻⁴ moles to about 2×10⁻³ moles, and even morepreferably from about 7×10⁻⁴ moles to about 1.5×10⁻³ moles per 100 partsby weight rubber.

Where silicon-containing curative is employed, a vulcanizing amount ofcurative preferably comprises from 0.1 to about 10 mole equivalents, andpreferably from about 0.5 to about 5 mole equivalents, of SiH percarbon-carbon double bond.

Generally, from about 5 to about 300 parts by weight, preferably fromabout 30 to about 250 parts by weight, and more preferably from about 70to about 200 parts by weight, of extender oil per 100 parts rubber isadded. The quantity of extender oil added depends upon the propertiesdesired, with the upper limit depending upon the compatibility of theparticular oil and blend ingredients; this limit is exceeded whenexcessive exuding of extender oil occurs. The amount of esterplasticizer in the composition will generally be less than about 250parts, and preferably less than about 175 parts, per 100 parts rubber.

Carbon black may be added in amount from about 40 to about 250, and morepreferably from about 40 to about 100 parts by weight per 100 parts byweight of rubber and thermoplastic material combined. The amount ofcarbon black that can be used depends, at least in part, upon the typeof carbon black and the amount of extender oil that is used. The amountof extender oil depends, at least in part, upon the type of rubber. Highviscosity rubbers are more highly oil extendable.

The thermoplastic elastomers may be prepared by using blending anddynamic vulcanization techniques that are well known in the art.Preferably, the thermoplastic elastomers are prepared in a one-stepprocess whereby the rubber, the LCB-plastic, and the optional linearthermoplastic resin are blended and the rubber is dynamically vulcanizedwithin the blend.

The term dynamic vulcanization refers to a vulcanization or curingprocess for a rubber contained in a thermoplastic elastomer composition,wherein the rubber is vulcanized under conditions of high shear at atemperature above the melting point of the polyolefin component. Therubber is thus simultaneously crosslinked and dispersed as fineparticles within the polyolefin matrix, although other morphologies mayalso exist. Dynamic vulcanization is effected by mixing thethermoplastic elastomer components at elevated temperature inconventional mixing equipment such as roll mills, Banbury mixers,Brabender mixers, continuous mixers, mixing extruders and the like.

Those ordinarily skilled in the art will appreciate the appropriatequantities, types of cure systems, and vulcanization conditions requiredto carry out the vulcanization of the rubber. The rubber can bevulcanized by using varying amounts of curative, varying temperatures,and a varying time of cure in order to obtain the optimum crosslinkingdesired.

The term vulcanized or cured rubber refers to an elastomeric polymerthat has undergone at least a partial cure. The degree of cure can bemeasured by determining the amount of gel, or conversely, the rubberthat is extractable from the thermoplastic elastomer by using boilingxylene or cyclohexane as an extractant. This method is disclosed in U.S.Pat. No. 4,311,628. By using this method as a basis, the cured rubber ofthis invention will have a degree of cure where not more than 35 percentof the rubber is extractable, preferably not more than 15 percent, evenmore preferably not more than 10 percent, and still more preferably notmore than 5 percent of the rubber is extractable. Alternatively, thedegree of cure may be expressed in terms of crosslink density.Preferably, the crosslink density is from about 40 to about 160 molesper milliliter of rubber. All of these descriptions are well known inthe as and described in U.S. Pat Nos. 5,100,947 and 5,157,081, which areincorporated herein by reference.

Despite the fact that the rubber component is partially or fully cured,the compositions of this invention can be processed and reprocessed byconventional plastic processing techniques such as extrusion, injectionmolding, and compression molding. The rubber within the thermoplasticelastomers of this invention is usually in the form of finely-dividedand well-dispersed particles of vulcanized or cured rubber, although aco-continuous morphology or a phase inversion is also possible.

The thermoplastic vulcanizates of this invention are useful for making avariety of molded and extruded articles such as weather seals, hoses,belts, gaskets, moldings, boots, elastic fibers and like articles. Theyare particularly useful for making articles by blow molding, extrusion,injection molding, thermo-forming, elasto-welding and compressionmolding techniques. More specifically, they are useful for makingvehicle parts such as weather seals, brake parts such as cups, couplingdisks, and diaphragm cups, boots such as constant velocity joints andrack and pinion joints, tubing, sealing gaskets, parts of hydraulicallyor pneumatically operated apparatus, o-rings, pistons, valves, valveseats, valve guides, and other elastomeric polymer based parts orelastomeric polymers combined with other materials such as metal/plasticcombination materials. Also contemplated are transmission beltsincluding V-belts, toothed belts with truncated ribs containing fabricfaced V's, ground short fiber reinforced V's or molded gum with shortfiber flocked V's. The thermoplastic vulcanizates of this invention arealso useful for making cellular articles such as weather seals. In fact,the superior properties of the cellular articles produced according tothis invention can replace rubber sponge in the most demanding weatherseal applications such as trunk and primary door seals in motorvehicles.

The thermoplastic vulcanizates of this invention can be foamed by usingconventional foaming procedures, which are well known in the art. Ingeneral, these procedures include (i) heating the thermoplasticvulcanizate to a temperature above the melting point of the LCB-plastic,linear plastic, or both, (ii) adding a blowing agent, and (iii)releasing the thermoplastic vulcanizate to atmospheric temperature andpressure. Depending on the type of blowing agent employed, the blowingagent may be added to the thermoplastic vulcanizate prior to heating thethermoplastic vulcanizate in the foaming process, although it ispreferred to add the blowing agent to the thermoplastic vulcanizatewhile it is in its molten state. Also, high pressure is typicallyrequired to prevent the foaming agent from prematurely expanding priorto releasing the thermoplastic vulcanizate to atmospheric temperatureand pressure. Where a chemical blowing agent is employed, the step ofheating should heat the thermoplastic vulcanizate and blowing agent highenough to trigger the chemical decomposition of the blowing agent.

In one embodiment, the thermoplastic vulcanizates of this invention arefoamed by using an extruder, such as a single or twin screw extruder.Upon releasing the thermoplastic vulcanizate from the extruder, theextrudate can be shaped, such as by extruding through a shaping die toform a profile. Alternatively, the thermoplastic vulcanizate can beinjected into a mold to produce a foamed thermoplastic part.

In one preferred embodiment, the thermoplastic vulcanizate is foamed byusing a single screw extruder that includes a two-stage shearing sectionthat includes spaced blisters and a homogenizing section between theblisters, and a homogenizing section downstream of the blisters. Byusing this extruder, water can be used as a blowing agent to producetechnologically useful foam profiles. This extruder and the method forits use are disclosed in U.S. Pat. No. 5,567,370, which is incorporatedherein by reference.

The foaming agents may include physical blowing agents, chemical blowingagents, or both. Preferably, the blowing agents should be soluble in thethermoplastic phase of the thermoplastic vulcanizate at the operatingconditions of temperature and pressure, i.e., while in the extruder, andphase separate at atmospheric pressure and ambient temperature, or at atemperature and pressure that is lower than the conditions within theextruder.

The physical blowing agents may include water, hydrocarbons such aspentane, propane and butane, fluorocarbons, hydrofluorocarbons,chlorofluorocarbons, hydrochlorofluorocarbons, nitrogen, and supercritical fluids such as carbon dioxide.

The physical blowing agents should be used in an amount from about 0.1to about 10 parts by weight, and preferably from about 0.5 to about 5parts by weight, based on the total weight of the thermoplasticvulcanizate and the blowing agent mixture.

In one preferred embodiment of this invention, water is used as ablowing agent. In this embodiment, from about 0.1 to about 10 parts byweight water is added per 100 parts by weight of the thermoplasticvulcanizate. In conjunction with the water, detergents, surfactants, orglycols such as ethylene glycol, may be used. This preferred process forfoaming the thermoplastic vulcanizatesis disclosed in U.S. Pat. No.5,070,111, which is incorporated herein by reference.

Chemical blowing agents include both exothermic and endothermic blowingagents. Examples of these chemical blowing agents include inorganicfoaming agents such as sodium hydrogen carbonate, sodium carbonate,ammonium hydrogen carbonate, ammonium carbonate and ammonium nitrite;nitrous compounds such as N,N′-dimethyl-N,N′-dinitrosoterephthalamideand N,N′-dinitrosopentamethylenetetramine; azo compounds such asazodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile,azodiaminobenzene and barium azodicarboxylate; sulfonylhydrazidecompounds such as benzenesulfonylhydrazide, toluenesulfonylhydrazide,p,p′-oxybis(benzenesulfonylhydrazide) anddiphenylsulfone-3,3′-disulfonylhydrazide; and azide compounds such ascalcium azide, 4,4′-diphenyldisulfonylazide and p-toluenesulfonylazide.Blends of the foregoing may also be employed such as blends of citricacid and sodium bicarbonate.

The chemical blowing agents should be used in an amount from about 0.5to about 10 parts by weight, and preferably from about 1 to about 7parts by weight, based on the total weight of the thermoplasticvulcanizate and the blowing agent mixture combined.

If necessary, a foaming assistant such as a nucleating agent may beadded. These nucleating agents are well known to those skilled in theart as disclosed in Thermoplastic Foams, by J. L. Throne, SherwoodPublishers, Hinckley, Ohio, 1996, which is incorporated herein byreference.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested as described in theGeneral Experimentation Section disclosed hereinbelow. The examplesshould not, however, be viewed as limiting the scope of the invention.The claims will serve to define the invention.

GENERAL EXPERIMENTATION Samples 1-17

Thermoplastic vulcanizates were prepared with long-chain branchedthermoplastic resins and compared to thermoplastic vulcanizates preparedwith linear thermoplastic resins. Table I provides the characteristicsof the five different LCB-plastic resins that were employed. MFR wasdetermined according to ASTM D-1238, condition L, under 2.16 Kg load at30° C. by using an appropriate capillary tube. The molecular weightswere determined by using GPC with the polymer dissolved in1,2,4-trichlorobenzene at 145° C., and the instrument calibrated withboth polystyrene and low molecular weight polyethylene standards.<g>_(w) was determined by using GPC MALLS (Multiple Angle Laser LightScattering), and <g>_(z) was determined by using GPC MALLS. <g>_(w) maybe obtained from the following equation:${\langle g\rangle}_{w} = \frac{\sum{C_{i}R_{gi}^{2}}}{\sum{C_{i}\left\lbrack {KM}_{i}^{\alpha} \right\rbrack}^{2}}$

where M_(i) is the molecular weight of the polymer, C_(i) is theconcentration of the polymer at molecular weight M_(i), R_(g) _(i) , isthe radius of gyration of the branched polymer at molecular weightM_(i), and K and α are measured constants from a linear polymer asdescribed by Paul J. Flory at page 310 of Principles of PolymerChemistry (1953), and the summation is over all the slices in thedistribution. Further, <g>_(z) of the entire polymer may be obtainedfrom the following equation:${\langle g\rangle}_{z} = \frac{\sum{C_{i}M_{i}R_{gi}^{2}}}{\sum{C_{i}{M_{i}\left\lbrack {KM}_{i}^{\alpha} \right\rbrack}^{2}}}$

where the variables M_(i), C_(i), R_(g) _(i) , K and α are as describedabove.

TABLE I LCB-Plastic LCB-Plastic LCB-Plastic LCB-Plastic LCB-PlasticLCB-Plastic I II III IV V VI M_(n)   69,000   63,400 107,475  62,935 52,041   107,100 M_(w)   425,300   391,100 272,682 237,068 202,906  604,100 M_(z) 1,301,000 1,188,000 619,647 571,027 459,749 1,601,000M_(w)/M_(n) 6.16 6.17 2.54 3.77 3.90 5.64 M_(z)/M_(w) 3.06 3.04 2.272.41 2.27 2.65 <g>_(w) — — 0.75 0.49 0.85 — <g>_(z) — — 0.59 0.65 0.75 —g′ @ MW > 1 × 10⁶ ≦0.55 ≦0.50 — — — ≦0.78 T_(m) (° C.) 160.87 161.80 —152.2 152.1 163.9 T_(c) (° C.) 129.42 129.93 — 107.7 108.9 — MFR(dg/min) 3.0 5.5 1.4 4.8 10 0.3 Diene (ppm) — — 375 300 200 0

LCB-Plastic I was obtained under the tradename PF814™ (Montell), andLCB-Plastic II was obtained under the tradename PF633™ (Montell).LCB-Plastic II, IV, and V were generally prepared as disclosed in U.S.Pat. No. 5,570,595, which is incorporated herein by reference.

The thermoplastic vulcanizates of Samples 1-9 included 100 parts byweight terpolymer rubber obtained under the tradename Vistalon™ (ExxonMobil), varying amounts of one of the LCB-plastics or a linearthermoplastic resin, 4.5 parts by weight phenolic resin (SchenectadyInternational; Schenectady, N.Y.), 2 parts by weight zinc oxide, 1.26parts by weight stannous chloride, 10 parts by weight clay (Burgess™),130 parts by weight, processing oil (Sunpar 150™), and 3.5 parts byweight wax (Sunolite™).

The thermoplastic vulcanizates of Samples 10-13 included mixing 100parts by weight terpolymer rubber obtained under the tradename Vistalon™(Exxon Mobil), varying amounts of one of the LCB-plastics or a linearthermoplastic resin, 6 parts by weight phenolic resin (SchenectadyInternational; Schenectady, N.Y.), 2 parts by weight zinc oxide, 1.26parts by weight stannous chloride, 10 parts by weight clay (Burgess™),107 parts by weight, processing oil (Sunpar 150™), and 3.5 parts byweight wax (Sunolite™).

The linear Resin I was obtained under the tradename DOO8M™ (AristechChemical Corp.), and was characterized by having an MFR of about 0.8dg/min., an M_(n) of about 88,000, an M_(w) of about 364,000, anM_(w)/M_(n) of about 4.13, and a melt temperature of about 167° C. Thelinear Resin II was obtained under the tradename 51S07A™ (Equistar), andwas characterized by having an MFR of about 0.7 dg/min., an M_(n) ofabout 112,651, an M_(w) of about 445,060, an M_(w)/M_(n) of about 3.95,and a melt temperature of about 168° C. Linear Resin III was obtainedunder the tradename PP4782™ (Exxon), and was characterized by having anMFR of about 1.9 dg/min, an M_(n) of about 108,691, an M_(w) of about387,924 and M_(w)/M_(n) of about 3.57 and a melt temperature of about168.

The rubber, the LCB-plastic or linear thermoplastic, and other additiveswere blended in a large-scale high shear mixer at a temperature of about120° to about 190° C. as described in U.S. Pat. No. 4,594,390, which isincorporated herein by reference.

Stress at 100 percent strain, tensile strength, and elongation at breakwere determined according to ASTM D-412 at 23° C. by using an Instrontesting machine. Weight gain was determined according to ASTM D-471after 24 hours at 125° C. Tension set was determined according to ASTMD-142, compression set was determined at 25% compression according toASTM D-395, and toughness was determined according to ASTM D-1292. ACRviscosity, which is a measure of the shear viscosity of a thermoplasticvulcanizate at a fixed shear stress, was measured by using an automatedcapillary rheometer that was equipped with a 33:1 L/D, 0.031 diameterorifice, at 204° C. and 118 kPa. Shore hardness was determined accordingto ASTM D-2240. Extensional viscosity was determined from melt strengthmeasurements by using a Rhestens Instrument from Goettfert Company,Germany.

Extrusion surface roughness was measured as described in ChemicalSurface Treatments of Natural Rubber And EPDM Thermoplastic Elastomers:Effects on Friction and Adhesion, Rubber Chemistry and Technology, Vol.67, No. 4 (1994). Spiral flow measurements were conducted as follows. Asample of dry thermoplastic vulcanizate is loaded into the hopper of a136 metric ton injection molding machine (Newbury H6-150ARS) having a 45mm screw diameter, a screw length/diameter ratio of 16:1 to 20:1, acompression ratio of 2.5:1, a maximum injection pressure of 1950 psi,and an initial inject timer with the capability of adjusting to 0.01seconds accuracy. Attached to the injection molding machine is a singlecavity spiral flow mold (Master Unit Die 84/90-001) equipped with a moldtemperature controller. The heat zones of the molding machine are set toachieve an actual melt temperature of about 195° C., both the initialinject and overall inject timers are set for three seconds, and the curetimer is set for 25-30 seconds. Other melt temperatures may be selecteddepending on the material. The injection pressure is adjusted accordingto the desired measurement, e.g., 450 psi, 950 psi, and 1,450 psi.Fifteen transition shots are molded into the single cavity spiral flowold and five samples are recorded for flow length and cavity pressures.

The amount of linear thermoplastic resin or LCB-plastic resin that wasused in each sample is provided in Table II along with the results ofthe physical testing of each sample.

TABLE II Samples 1 2 3 4 5 6 7 8 9 10 Linear Plastic I 41 — — — — 10 20— — — Linear Plastic II — 41 — — — — — — — — Linear Plastic III — — — —— — — — — — LCB Plastic I — — 41 — — — — — — — LCB Plastic II — — — 41 —— — — — — LCB Plastic III — — — — 41 31 21 — — — LCB Plastic IV — — — —— — — 41 — 51 LCB Plastic V — — — — — — — — 41 — Shore A Hardness 66 6554 54 54 57 60 55 56 66 Shore D Hardness — — — — — — — — — — UltimateTensile Strength (MPa) 6.55 5.74 4.53 4.5 3.28 3.49 5.25 3.43 3.55 5.91Elongation at Break (%) 465 342 293 287 239 250 382 273 377 334 M 100(MPa) 2.37 2.62 1.87 1.83 1.82 1.94 2.03 1.84 1.88 2.61 % Weight Gain101 90 116 118 131 121 121 119 115 65 ACR Viscosity @ 204° C. (Poise)367 242 9,089 10,580 9,009 1,234 818 5,733 1,200 146 ExtensionalViscosity @ 190° C. (MPa) 0.0606 0.111 Fell Apart Fell Apart 0.12 0.1450.097 0.114 0.0884 — ESR (Ra) 117 71 497 297 >400 163 129 329 198 39Spiral Flow (Ins.) 28.1 27.4 15.3 15.8 16.6 18.8 21.8 18.3 21.8 — Inches@ 400 F. @ 950 (MPa) Tension Set @ 24° C. (%) 10 12.5 5 5 6 6 7.5 6 6 10Compression Set (%) 70° C. @ 22 Hrs 26 26 19 19 20 22 24 19 20 —Compression Set (%) 100° C. @ 22 Hrs 27 28 22 22 22 24 25 20 23 —Samples 11 12 13 14 15 16 17 Linear Plastic I — — — — — — — LinearPlastic II 50 — — — 229 — — Linear Plastic III — 50 — — — — — LCBPlastic I — — 50 — — 229 — LCB Plastic II — — — 50 — — 229 LCB PlasflcIII — — — — — — — LCB Plastic IV — — — — — — — LCB Plastic V — — — — — —— Shore A Hardness 67 70 59 59 — — — Shore D Hardness — — — — 43 42 41Ultimate Tensile Strength (MPa) 5.87 6.33 4.12 3.76 16.22 16.00 18.06Elongation at Break (%) 243 258 208 208 434 339 384 M 100 (MPa) 3.112.83 2.56 2.45 9.94 10.72 11.49 % Weight Gain 104 114.5 100.5 106.5 6285 87 ACR Viscosity @ 204° C. (Poise) 985 485 2,747 2,159 2,535 583 545Extensional Viscosity @ 190° C. (MPa) 0.189 0.141 0.0825 — — — — ESR(Ra) 520 486 273 285 — — — Spiral Flow (Ins.) 21 25 18 19 — — — Inches @40° F. @ 950 (MPa) Tension Set @ 24° C. (%) 12.5 11.5 5 6 32 26 27Compression Set (%) 70° C. @ 22 Hrs 43 47 30 28 — — — Compression Set(%) 100° C. @ 22 Hrs — — — — — — —

Samples 18-23

In a similar fashion to Samples 1-13, additional thermoplasticvulcanizates were prepared with linear thermoplastic resins or blends oflinear thermoplastic resins and LCB-plastic resins. LCB-Plastic VI, thecharacteristics of which are described above, was obtained under thetradename Profax™ SD613 (Montell). This material was furthercharacterized by a shear viscosity at 1 s⁻¹ and 180° C. of 20 kPa·s, andan extensional viscosity at 0.1 s⁻¹ strain rate and 180° C. of 2×10⁵Pa·s at 10 seconds and 6×10⁵ Pa·s at 35 seconds. LCB-Plastic VII wasobtained under the tradename HMS 130D™ (Borealis). This polymer wascharacterized by a shear viscosity at 1 s⁻¹ and 180° C. of 4.5 kPa·s,and an extensional viscosity at 0.1 s⁻¹ strain rate and 180° C. of 4×10⁴Pa·s at 10 seconds and 1×10⁶ Pass at 35 seconds.

The thermoplastic vulcanizates of Samples 18-23 included mixing 100parts by weight terpolymer rubber obtained under the tradename Vistalon™(Exxon Mobil), varying amounts of linear thermoplastic resin or blendsof linear thermoplastic resin and LCB-plastic resin, 4 parts by weightphenolic resin (Schenectady International), 2 parts by weight zincoxide, 1.5 parts by weight stannous chloride, 10 parts by weight clay(Icecap™), and 150 parts by weight processing oil (Sunpar 150™). Thelinear thermoplastic resin employed was obtained under the tradenameD008M(Aristech), and was characterized by having an MFR of about 0.8dg/min., an M_(n) of about 88,000, an M_(w) of about 364,000, anM_(w)/M_(n) of about 4.13, and a melt temperature of about 161° C.

The amount of linear thermoplastic resin and LCB-plastic resin used ineach sample is provided in Table III along with the results of physicaltesting of each sample.

TABLE III Samples 18 19 20 21 22 23 Linear- 42 32 16 24 16 24Thermoplastic Resin LCB-Plastic — — 16 8 — — Resin VI LCB-Plastic — — —— 16 8 Resin VII Shore A 66 60 57 60 60 60 Hardness ACR Viscosity 353310 382 443 413 461 (Poise) Ultimate Ten- 6.9 5.6 6.14 5.7 4.57 5.18sile Strength (MPa) Modulus at 2.71 2.63 2.54 2.65 1.83 1.79 100% (MPa)Elongation at 520 368 397 365 332 380 Break (%) % Weight Gain 116.7 82.589.5 87 73.5 87 24 hrs at 125° C. Extensional 152 222 152 193 132 204Viscosity (kPa · s) ESR (Ra) 66 60 72 61 61 77 Tension Set @ — 7.5 5 8.58.5 6 24° C.

The thermoplastic vulcanizates prepared in Samples 18-23 were foamedinto profiles. This was accomplished by using a six-zone, 60 mmdiameter, single-screw extruder having a 30:1 L/D. The thermoplasticvulcanizate was fed at a rate of about 15-40 kg per hour in conjunctionwith from about 90 to about 500 ml of foaming agent per hour, where thefoaming agent was injected between zones 4 and 5. At the exit end of theextruder, the extrudate was released through a bulb profile die with awall thickness of 1 mm. A pressure of at least 2.5 MPa was experiencedat the die head, and the foaming agent (water) was injected at about14-20 MPa. When used, the chemical foaming agent was obtained under thetradename Hydrocerol™ (Clariant; Charlotte, N.C.) Each temperature zonewas set to a temperature between about 160° C. and about 200° C.

The extruded cellular profiles were subjected to physical testing.Specific gravity was determined according to Archimede's method,extrusion surface roughness (Ra) was determined as described above,water absorption was determined according to ASTM D1056, compression setwas determined by using a test method similar to ASTM D395-89 after 22hours at 100° C., and compression load deflection was determined asfollows. A 100 mm sample is uniformly compressed to 40% of its height atroom temperature for three times and the third force measurement isreported as the compression load deflection. The results of thisphysical testing are provided in Table IV.

TABLE IV Samples 18 19 20 21 22 23 Foam Specific Gravity — 0.48 0.560.48 0.57 0.51 (1.1 wt % H₂O) Foam Specific Gravity (1.4 wt 0.45 0.40.51 0.45 0.46 0.43 % H₂O) ESR (Ra) in μm 9.1 8.5 9.3 8.8 9.3 8.6 WaterAbsorption Atmos- — 6.1 3.8 5.4 4.4 6.0 pheric (wt %) Water AbsorptionVacuum — 31.4 18.9 31.7 26.8 40.3 (wt %) Compression Set 22 hrs @ 5238.6 34 32.8 35 35.5 100° C. (%) & 40% compression Compression LoadDeflection 0.77 0.44 0.75 0.36 0.42 0.36 (Kgf/100 mm)

While the best mode and preferred embodiment of the invention have beenset forth in accord with the Patent Statues, the scope of this inventionis not limited thereto, but rather is defined by the attached claims.Thus, the scope of the invention includes all modifications andvariations that may fall within the scope of the claims.

What is claimed is:
 1. A thermoplastic vulcanizate comprising avulcanized rubber within a mixture that includes from about 15 to about90 percent by weight of the rubber and from about 10 to about 85 percentby weight of a long-chain branched thermoplastic resin, where saidlong-chain branched thermoplastic resin is (i) an α-olefin polymer, (ii)a copolymer of an α-olefin and an α-ω-olefin diene, or (iii) a mixturethereof, where the long-chain branched thermoplastic resin ischaracterized by a <g′>_(vis) from about 0.2 to about 0.95, and a meltflow rate from about 0.3 to about 30 dg/min.
 2. The thermoplasticvulcanizate of claim 1 containing from about 27 to about 40 percent byweight of said long-chain branched thermoplastic resin based upon thetotal weight of the vulcanized rubber and the long-chain branchedthermoplastic resin.
 3. The thermoplastic vulcanizate of claim 2, wherethe vulcanized rubber has a crosslink density from about 40 to about 180moles per milliliter of rubber.
 4. The thermoplastic vulcanizate ofclaim 2, where the vulcanized rubber has a degree of cure where not morethan 15 percent of the rubber is extractable in boiling xylene orcyclohexane.
 5. The thermoplastic vulcanizate of claim 1, where thelong-chain branched thermoplastic resin has a weight average molecularweight from about 100,000 to about 600,000, a number average molecularweight from about 40,000 to about 200,000, and a z-average molecularweight from about 400,000 to about 2,000,000.